1. Field of the Invention
The present invention relates to a substrate with a protective film used for manufacturing an optical memory device represented by an optical card or an optical disc, and a method of manufacturing an optical memory device using the same.
2. Description of the Prior Art
A conventional substrate with a protective film for manufacturing an optical memory device (merely referred to as substrate 10 hereinafter) will be described with reference to FIGS. 3 and 5.
A ROM type optical memory device used for reproduction (i.e. read only) is commercialized as a CD (compact disk), a CD-ROM (compact disk read only memory), and a VD (video disk). In addition, the development of a writable and erasable optical memory device has proceeded rapidly.
An optical memory device such as an optical card is a substrate 10 having recording layers 111 serving as recording regions formed thereon. Laser light or the like is applied to the recording layers 111 to carry out reading or recording (see U.S. Pat. No. 4,544,835 and No. 4,680,460).
Both surfaces 11 and 12 of the substrate 10 on which the recording layers 111 are formed for an optical memory device are respectively covered with protective films 21 and 22. The protective films 21 and 22 are used for protecting the surfaces 11 and 12 of the substrate 10 from being damaged before the recording layers 111 are formed.
This substrate 10 is fed into an optical memory device manufacturing apparatus after the protective films 21 and 22 are stripped therefrom (see FIG. 3(a)). The substrate 10 is then fed to a recording layer forming process station 50 after only portions, corresponding to the recording layers 111 to be formed on the substrate 10, of the substrate are covered with a mask 30 provided with openings in the manufacturing apparatus. In this recording layer forming process station 50, the recording layers 111 are formed on the surface 11 of the substrate 10 (see FIG. 3(b)). Thereafter, the substrate 10 becomes an optical memory device through a plurality of processes such as a guide track forming process station 51 (see FIG. 3(c)) for forming guide tracks, a cutting process station 52 (see FIG. 3(c)) using a cutter, and a protective layer forming process station (not shown) for forming a protective layer 13 made of transparent synthetic resins.
Furthermore, when the recording layers 111 are formed without covering the surface 11 of the substrate 10 with the mask 30, the recording layers 111 are formed over the entire surface of the substrate 10 as shown in FIG. 5. Thus, even if the protective layer 13 is formed on the recording layers 111, the recording layers 111 are directly exposed to the external air along the edges of the substrate 10. Accordingly, the substrate 10 becomes an optical memory device that is inferior in resistance to the enviroment.
Since the above described conventional mask is formed like a plate, optical memory devices can not be continuously manufactured from a longitudinal sheet-like substrate such as a flexible substrate. In addition, if the mask is not used, the substrate 10 becomes an optical memory device that is inferior in resistance to the environment as described above. More specifically, in the conventional substrate with a protective film for manufacturing an optical memory device, the mask is an indispensable element. Accordingly, the manufacture of optical memory devices using the conventional substrate with a protective film for manufacturing a conventional optical memory device is low in production efficiency, making it difficult to reduce costs.